446 A MANUAL OF BACTERIOLOGY 



heat and carbolic acid, (6) cultivation on agar and treat- 

 ment with carbolic acid. 



Besredka l claims that an immediate and lasting (six 

 months) immunity may be produced by making a mixture 

 of cholera culture and cholera-immune serum, allowing this 

 to stand for twelve hours, heating to 56 C. for one hour 

 and then injecting subcutaneously. 



Strong 2 prepares a vaccine from autolysed cultures. 

 The cholera vibrio is grown on surface agar for twenty- 

 four hours at 37 C. ; the growth is then washed off with 

 sterile water, the suspension is kept at 60 C. for twenty- 

 four hours, and then at 37 C. for two to five days, and is 

 finally filtered through a porcelain filter. 



Clinical Diagnosis 



Some of the rice-like flakes should be picked out of the stool and 

 well rinsed in sterile salt solution. 



1. From one of the whitish, slimy, rice-like flakes in the evacua- 

 tions or the intestine films are prepared, stained with Loffler's blue, 

 washed, dried, and mounted. If on examination large numbers of 

 curved rods lying in groups parallel to one another are observed, 

 the diagnosis of Asiatic cholera may be made with some degree of 

 certainty. Koch states that this is so in quite half the cases, 

 especially the acute ones. (Single, or a few, vibrios are of no 

 diagnostic significance ; they may occur in normal and diarrhrea 

 stools. The presence of numbers of vibrios having the " fish-in - 

 stream " arrangement is also not absolutely characteristic.) 



2. Gelatin and agar plates should be prepared from an emulsion 

 of rice-like flakes. Agar plates are best prepared by smearing the 

 flake over the surface of the solidified agar. The plates are incubated 

 at 22 C. and 37 C. respectively. In the gelatin plates the charac- 

 teristic colonies of the cholera vibrios should be recognisable in 

 about twenty-four hours, in the agar plates in from twelve to 

 sixteen hours. The likely colonies should be examined microsco- 

 pically and peptone-water and other cultures prepared from them. 



A better medium to employ is Dieudonne's blood alkali agar. 



1 Ann. de VInst. Pasteur, 1902, p. 918. 



2 Bureau of Gov. Laboratories, Manila, Bull. No, 16, 1904 (Bibliog.). 



